The present invention relates to an electronic control circuit for controlling generator output, which is accommodated in a vehicle-mounted A.C. generator, and is in the form of a monolithic IC chip on a ceramic substrate.
Heretofore, as a controller, for an A.C. generator in a vehicle in which discrete components are employed as circuit elements to be mounted onto a wiring board, a controller is known which has a circuit configuration shown in FIG. 3. This controller includes: an A.C. generator 1 having an armature coil 101 for driving an engine and for starting the generating operation of electrical energy, and a field coil 102; a rectifier 2 for taking out an output of generating electrical energy from the armature coil 101 to rectify the output, which is supplied to batteries 4 or to an electrical load (not shown); and a controller 3 having a voltage regulator 3a for detecting the voltage developed across the terminals of the batteries 4 to adjust the output voltage of the A.C. generator 1 on the basis of the voltage thus detected and a field current restricting unit 3b for detecting the field current caused to flow through the field coil 102 to restrict the field current on the basis of the detected current.
Reference numeral 5 indicates a key switch for starting the engine. This key switch 5 is turned ON so that the current flows through the field coil 102 from the batteries 4 to carry out the initial excitation.
The voltage regulator 3a is configured in such a way as to include: a constant voltage circuit in which an operating resistor 301 and a Zener diode 302 are electrically connected in series between the positive electrode of the batteries 4 and the earth through the key switch 5 to fetch a constant voltage A, which is determined on the basis of the breakdown voltage of the Zener diode 302, from a connection point P between the operating resistor 301 and the Zener diode 302; a voltage dividing circuit having voltage dividing resistors 303 and 304, which are electrically connected in series between an output terminal 201 of a positive electrode and an output terminal 202 of a negative electrode of the rectifier 2 to divide the output voltage of the rectifier 2; a first comparator 307 for applying a divided voltage Vd from the voltage dividing circuit to an input terminal (xe2x88x92) of the negative side and for applying a fixed reference voltage VREF1 to an input terminal (+) of the positive side to make H or L the logical level at the output terminal in accordance with the magnitude relationship between the divided voltage Vd and the reference voltage VREF1; an output transistor 311 which is turned ON at the time when the logical level at the output terminal of the first comparator 307 has become H to cause the field current to flow through the field coil 102 from the batteries 4; a suppression diode 310 which is electrically connected in reverse between a positive side line and a collector of the output transistor 311 to suppress a surge current which occurs at the time when shutting off the field current; and a base resistor 309 which is electrically connected between the output side of the key switch 5 and the base of the output transistor 311 to restrict a base current which is caused to flow through the base of the output transistor 311 at the time when carrying out the initial excitation of the field coil 102.
The field current restricting unit 3b includes: a voltage dividing circuit having voltage dividing resistors 305 and 306 for dividing a constant voltage A at a predetermined resistance ratio to generate a predetermined reference voltage VREF2; a field current detecting resistor 312 connected between an emitter of the output transistor 311 and the earth for converting the field current flowing through the emitter into a voltage V1 to detect the voltage V1 thus obtained; and a second comparator 308 for applying the reference voltage VREF2 to an input terminal (+) of the positive side and for applying the voltage V1 to an input terminal (xe2x88x92) of the negative side to make L the logical level at the output terminal at the time when the voltage V1 has become higher than the reference voltage VREF2.
Now, the description hereinbelow will be given with respect to the outline of the operation in the conventional controller for an A.C. generator for a vehicle.
After having started the engine, the divided voltage Vd as a criterion of the terminal voltage of the batteries 4 rises above the reference voltage VREF1 to provide the over-charging state, the logical level at the output terminal of the first comparator 307 goes to L to turn OFF the output transistor 311 so that the field current to the field coil 102 is shut off, which reduces the output of the electrical energy generation.
When the terminal voltage of the batteries 4 has been reduced and also the divided voltage Vd has become lower than the reference voltage VREF1, the logical level at the output terminal of the first comparator 307 goes to H to turn ON the output transistor 311. As a result, the current flowing loop consisting of the batteries 4, the field coil 102, the output transistor 311, the field current detecting resistor 312, and the earth is formed so that the field current is caused to flow from the batteries 4 to the field coil 102 to carry out the generation of electrical energy, and also the output of the generation of electrical energy is rectified through the rectifier 2 to be supplied to the batteries 4 which are in turn charged with the fixed voltage 14.5 V for example.
In this way, the output transistor 311 is turned repeatedly ON/OFF in accordance with the drop and the rise of the voltage developed across the terminals of the batteries 4 to intermittently control the field current to so that the terminal voltage is maintained at a fixed value.
The surge current which is generated through the field coil 102 along with the interruption of the field current is suppressed by the suppression diode 310 to mitigate the influence thereof exerted on the electronic circuit.
However, if the line through which the terminal voltage of the batteries 4 is detected is cut in the voltage regulator 3a so that the divided voltage Vd becomes zero, for example, then the logical level of the output of the first comparator 307 continues to be H, and hence the A.C. generator 1 starts to cause to flow the excessive field current through the output transistor 311 in order to make the divided voltage Vd the reference voltage VREF1.
At this time, the field current is caused to flow through the field current detecting resistor 312 to generate the voltage drop of the voltage V1. Then, the voltage V1 is applied to the negative side input terminal (xe2x88x92) of the second comparator 308. The reference voltage VREF2 which is used to judge the excessive field current is applied to the positive side input terminal (+) of the second comparator 308. At the time when the voltage V1 has become higher than the reference voltage VREF2, the logical level at the output terminal of the second comparator 308 goes to L.
For this reason, the output at the logical level H of the first comparator 307 is absorbed by the output terminal of the second comparator 308, whereby the base current of the output transistor 311 is shut off, and the field current is also shut off to stop the generation of electrical energy to prevent the burning of the A.C. generator.
If the discrete components such as resistors, capacitors and semiconductor devices are mounted onto the printed board as in the method of mounting the electronic apparatus in the conventional controller, then a large mounting area is required and the scale of the whole controller becomes large.
In addition thereto, since the high accuracy is required for the output control of the vehicle A.C. generator along with the promotion of the electronics for the vehicle control, the complexity and the high density of the electronic circuit in the controller are unavoidable.
Therefore, in the case where the discrete components are mounted to the printed board to configure such an electronic circuit, there arises the inconvenience that the scale of the whole controller becomes so large as to restrict the miniaturization of the A.C. generator.
In the light of the foregoing, the present invention has been made in order to solve the above-mentioned problems associated with the prior art, and hence it is therefore an object of the present invention to obtain a controller for an A.C. generator in which the circuit board can be miniaturized and the difficulty of building the circuit board into the body of the A.C. generator is removed, and also a constant of a field current detecting resistance can be readily changed in correspondence with the field current of the A.C. generator.
1. The present invention includes: batteries each of which is charged with electric charges on the basis of an output of generation of electrical energy of an A.C. generator having a field coil; voltage regulating means for regulating a current, which is caused to flow through the field coil, on the basis of the detection result of a voltage developed across the terminals of the batteries due to an output voltage of the A.C. generator into an fixed output value of generation of electrical energy of the A.C. generator; and field current restricting means for detecting a current flowing through the field coil by means of a field current detecting resistor, which restricts the current to a predetermined value in correspondence to the detection result, wherein the field current detecting resistor is formed in the form of a thick film printed resistor, and with respect to each of the means other than the thick film printed resistor, electronic circuits are configured in the form of an integrated circuit.
2. According to the present invention, the thick film printed resistor and the integrated circuits are formed on an insulating board.
3. According to the present invention, a resistor body constituting the thick film printed resistor is trimmed to adjust the resistance value thereof and to adjust the field current detection value.
4. According to the present invention, failure alarm means for detecting a failure of the A.C. generator on the basis of the output of the A.C. generator to give an alarm is provided in the form of an integrated circuit.